The present invention relates generally to processing of three-dimensional, 3D, images. More particularly the invention relates to an image handling system according to the preamble of claim 1 and a corresponding method. The invention also relates to a computer program product and a processor-readable medium.
In some types of 3D imaging, especially in the medical field, it is important that one can identify one or more particular items in both a first image, a second image and any subsequent images of an object/subject. For example, a patient's liver may be defined in a first computer tomography, CT, image registered prior to performing a radiation therapy session. Then, a physician is interested in examining the effects of the therapy. To this aim, it is important that the liver can be adequately identified in a second image registered after the therapy session. In the second image, the liver may have a different shape than in the first image. Presuming that tumorous tissue to be treated is located in the liver, the irradiation, as such, will probably have deformed the organ somewhat. However, the mere fact that the gastric contents is different, the patient has a slightly different position and/or that different imaging equipment was used when registering the second image may also explain why a deformation has occurred. In any case, it is normally a far from trivial task to identify the volume boundaries of an organ, e.g. a liver, in a second image on the basis of an identification made in a corresponding first image. Since the data set is in 3D, the identification of an organ or structure is often a manual process, wherein an operator has to define the relevant boundary in a respective image plane—segment per segment through the entire volume of interest.
WO 2012/069965 describes a radiation therapy planning system including a planning module, which receives a first planning image set from a diagnostic imaging apparatus and uses automatic segmentation tools or manual segmentation tools and a radiation therapy planning system to generate a first radiation therapy plan. After the first radiation therapy plan has been applied for one or more therapy sessions, a second planning image set is generated. The planning module uses a deformable image registration algorithm to register the planning image set and generate a corresponding deformation map which is applied to segmented objects of interest, OOIs, of the segmented first planning image set to propagate the objects of interest onto the second planning image set. The deformation map is corrected in accordance with deviations between the propagated and actual OOI locations in two steps: 1) manual and/or automated corrections of the propagated OOIs are performed, such as region of interest contour corrections and/or landmark point of interest positions; 2) a corrected global deformation map is generated from these local OOI corrections. The corrected deformation map is applied to the first radiation therapy plan and an accumulated radiation map depicting the radiation accumulated in each OOI during the therapy session(s) implemented with the first radiation therapy plan.